The climate-change campaign against fossil fuels has been having a hard time with democracy. Voters in the U.S. support fracking and the Keystone XL pipeline, Australia repealed its carbon tax, and frustration with green energy costs is rising across Europe. So perhaps it’s not surprising that President Obama has turned to a dictatorship for help with his anticarbon ambitions.

In that sense, the emissions accord sealed Tuesday night between the U.S. and China is a perfect reflection of the mindset of Western climate-change activists. Cheap and abundant energy is popular among Americans because it raises living standards and helps the economy grow.

The romance of the fresh princelings of Beijing is that they needn’t abide such barriers to enlightened governance as elections, a free press, transparency, the rule of law and two political parties. They can simply order economic transformation in the next five-year plan, and censor any dissenters as Al Gore wants to do in the U.S. Thus in China Mr. Obama has found the ideal climate-change partner: A technocratic elite that can instruct the bourgeoisie how they must light their homes and commute to work.

We and many others have been skeptical of a U.S.-China carbon pact, though that was because we assumed the White House and green lobby would demand terms that imposed at least some discipline on Chinese behavior. We discounted the possibility that Mr. Obama preferred the illusion of progress, and that his green allies could be rolled as cheaply as the terms of Tuesday’s accord.

Under the nonbinding, no-detail agreement, Supreme Leader Xi Jinping promises “to intend to achieve the peaking of CO2 emissions around 2030,” and then maybe after that to decline. This is another way of describing the status quo.

Forecasts from the U.S. Energy Information Administration, BP ’s Statistical Review of World Energy and the academic journal Energy Policy all expect Chinese energy consumption to crest in two decades due to demographic and urbanization trends. Mr. Obama has in essence persuaded the Chinese to do what they planned to do anyway.

Mr. Xi also agreed to shift at least 20% of Chinese energy production to non-fossil-fuels by 2030. But this too is what China has already intended, albeit largely by replacing dirty coal with nuclear power. China’s Communist Party has relied on coal to fuel rapid economic growth but that is increasingly becoming a political liability as the air becomes unbreathable. Then there is widespread groundwater contamination and an eat-at-your-own-risk food supply.

This tangible damage has inspired a revolt against the corruption and eyes-wide-shut ecological denial that defines China’s political system. The harm—measured in health problems and premature deaths, not merely higher temperatures predicted decades away in climate computer models—also should remind America’s green central-planners that autocracies are the world’s worst polluters. Think of the death of the Aral Sea under the Soviets, or dead pigs floating down the Yangtze.

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All of which suggests that this accord is less about China than American climate politics. One of the main arguments against U.S. carbon rationing has been that such economic masochism is pointless as long as Chinese and Indian emissions continue to grow. Mr. Obama will now claim the Middle Kingdom is signed onto his anticarbon agenda, even if its promises are distant and vague.

In return for Mr. Xi’s assurances, Mr. Obama pledged that the U.S. will cut emissions by as much as 28% below 2005 levels by 2025. This implies doubling the annual pace of CO2 reductions over the 17% marker that Mr. Obama set in 2009. So using the Sino-American deal as cover, Mr. Obama will now say he is obliged to impose a new burst of aggressive carbon regulations, no matter the harm to U.S. growth.

The difference is that American governance, unlike China’s, is supposed to follow the rule of law; companies can’t refuse to obey regulations because the CEO’s brother-in-law belongs to the Party. Yet most of the rule-makings to enforce Mr. Obama’s promises to China will emerge from his administrative-state tunnels like the Environmental Protection Agency without a vote in Congress. Under this President, the political systems of the East and West may share more features than patriots care to admit.

This condominium between the world’s No. 1 and No. 2 carbonizers is also supposed to inspire a new global climate treaty in Paris next year, but other nations may draw a different lesson about Mr. Obama’s negotiation methods. The Chinese no doubt saw how much the President wanted an agreement and that he would accept nearly anything that could pass as one.

Meaningless global warming promises are much easier than corralling weapons of mass destruction in North Korea, or convincing Beijing to fight Islamic State, or for that matter stopping Chinese cyber-attacks on U.S. military and corporate targets. Mr. Xi must have been delighted to see a U.S. President agree to make America less economically competitive in return for rhetorical bows to doing something someday about climate change.